Up to the present many catalysts for polymerization and copolymerization of olefins along with polymerization processes have been reported. However, the properties of polymers produced by a catalyst depend greatly upon the properties of the catalyst. It is desirable to develop an improved catalyst suitable for producing a polymer having a particular required physical property.
In catalysts for gaseous polymerization control of the shapes, sizes, and the size distribution of the catalyst is very important to ensure a good commercial workability. A catalyst having smaller particle size may cause problems during its transit, so it is necessary to minimize the particle size by producing a catalyst of narrow particle size distribution. For example, in order to produce heterophasic copolymers of 1000 .mu.m in size with high ethylene content, especially for impact resistant applications, a large catalyst particle size of about 30 .mu.m to about 50 .mu.m is generally required for the polymerization. Furthermore, for copolymerization of olefins, a catalyst with a greatly developed system of pores in its structure is extremely advantageous. Finally, a catalyst needs to be excellent in its mechanical properties, so as to resist wear during the polymerization process and to ensure a good bulk density of the polymer produced. The important thing in the development of a polymerization catalyst is, therefore, the provision of a process for production of a catalyst which allows control and adjustment of the structures and sizes of the catalyst's particles and particle size distribution, and yet remains a necessarily simple process.
Numerous olefin polymerization catalysts containing magnesium and based on titanium and production processes utilizing them have been reported, and these are suitable for gaseous polymerization.
Methods which make use of magnesium solutions for the production of catalysts are known. For instance, a magnesium solution may be produced by reacting a magnesium compound, in the presence of a hydrocarbon solvent, with such electron donors as alcohols, cyclic ethers, etc. Use of an alcohol as an electron donor is mentioned in U.S. Pat. No. 4,330,649 and Japanese Patent Pub. Sho 58-83006. In U.S. Pat. Nos. 4,315,874, 4,399,054, 4,071,674, and 4,439,540, methods are also reported for the production of magnesium solutions. Use of a silicon compound as a constituent of the catalyst for obtainment of solid catalyst components from magnesium solutions has been described in U.S. Pat. Nos. 4,071,672, 4,085,276, 4,220,554, 4,315,835, etc.
U.S. Pat. Nos. 4,946,816, 4,866,022, 4,988,656, 5,013,702, and 5,124,297 are all mutually related, and the processes for producing catalysts in these patents comprise (i) making a solution containing magnesium from a magnesium carboxylate or magnesium alkylcarbonate, (ii) precipitating magnesium in the presence of transition metal halide and an organosilane, (iii) reprecipitating the once precipitated solid components by the use of a mixed solution containing tetrahydrofuran, and (iv) producing a catalyst of uniform size distribution by reacting the reprecipitated particles with transition metal compounds and electron donor compounds. These processes tend to require too many steps in the production of the catalyst. These processes also tend to involve production processes which are themselves a little too complicated.
Japanese Patent Publication Sho 63-54004 and U.S. Pat. No. 4,330,649 describe processes in which the magnesium solution is produced by reacting a magnesium compound with more than one member of the group consisting of alcohol, organic carboxylic acid, aldehyde, and amine in the presence of an organic hydrocarbon solvent, with the final catalytic component being produced by reaction of the above solution with titanium compounds and an electron donor. Organosilane, mentioned as a shape-controlling agent in the patents cited above, has often been used in the process of production of solid catalysts. Use of this shape-controlling agent is helpful in adjusting the particle size distribution of catalysts by restraining generation of either very small or very large granules. Such an organosilane is a material represented by a general formula, R.sub.n SiR'.sub.4-n (n=0, 1, 2, 3, or 4), in which R represents a hydrogen, alkyl, alkoxy, haloalkyl, or aryl group having from one to 10 carbon atoms; R' represents OR or halogen. Examples of organosilanes include trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, tetraethoxysilane, tetrabutoxysilane, and others. To our knowledge, no prior art has been reported that organosilanes were applied for the purpose of increasing the porosity of catalysts.